Touch buttons have become a normal part of modern electronic devices. Smartphones, tablets, control panels, appliances, cars, and many other products now rely on flat touch-sensitive surfaces instead of traditional mechanical buttons.
While these interfaces look clean and modern, they have one important limitation: they do not physically “click.”
A mechanical button gives users several types of feedback at once. You can feel the button move, sense a small vibration, and often hear a click. This combination makes it clear that an action has been registered.
Now, Quang Van Duong and his team have developed a new type of extremely thin, or “skinny,” touch button that can bring this experience back. The technology can generate both haptic vibrations and audible sounds from the same thin structure, potentially making virtual touch buttons feel much more like physical buttons.
Why Touch Buttons Lack the Traditional Click
Mechanical buttons are effective because they naturally provide multiple forms of feedback. When pressed, they produce a physical force, a tactile sensation, and usually an audible click.
Touch buttons work differently. Capacitive, resistive, and inductive sensors can detect a finger without requiring mechanical movement. This makes devices thinner and gives designers more freedom, but the physical sensation of pressing a button is largely lost.
Manufacturers have tried to solve this problem using sounds or vibrations.
Artificial beep sounds can tell users that their touch was detected. Vibrating motors and piezoelectric actuators can provide haptic feedback. However, conventional vibration systems often struggle to create localized feedback for many different buttons on a flat surface.
Another approach uses electrovibration or ultrasonic vibration. But these methods generally depend on the user's fingertip moving across the surface.
The researchers wanted to solve a different problem: Can a touch button produce a localized “click-like” vibration even when the finger simply presses down on it?
Their answer uses a special polymer film.
The Special Polymer Behind the Button
At the heart of the new device is a material called a relaxor ferroelectric polymer, or RFP.
The researchers used a blend of two polymers:
P(VDF-TrFE-CFE) at 80% by weight
P(VDF-TrFE) at 20% by weight
This combination can produce a large change in shape when exposed to an electric field. This phenomenon is known as electrostriction.
Some relaxor ferroelectric polymers can generate electrostrictive strains approaching about −7% under an electric field of 150 V/µm.
That ability to deform significantly is important because the polymer can turn electrical signals into mechanical movement.
The researchers use this movement to create the vibration that the user feels—and, at higher frequencies, the sound that the user hears.
How the Skinny Button Works
The button is built from several thin layers.
A flexible touch layer contains a scratch-resistant cover film, a touch sensor, a top electrode, and the RFP film. A bottom electrode is positioned on the substrate below it.
A thin spacer creates a controlled air gap between the RFP film and the bottom electrode.
The electrodes are designed as ribbon-shaped sections. This arrangement divides the polymer into different active regions that can be controlled using electrical signals.
When a person presses the button with a fingertip, the pressure brings the relevant parts of the structure into contact or close interaction.
This creates a localized electric field beneath the finger.
The electric field causes the RFP film to deform through electrostriction. That deformation produces mechanical movement in the flexible touch layer.
The researchers call the resulting vibration behavior fretting vibration.
The important part is that the contact area created by the fingertip helps amplify the vibration. In other words, a relatively small pressing action can produce a stronger localized mechanical response.
One Button Can Produce Touch and Sound
The most interesting feature is that the same skinny button can provide different forms of feedback depending on the electrical signal applied to its electrodes.
At frequencies around 50 to 300 Hz, the vibration falls into a range that can be perceived as tactile feedback.
The user can therefore feel a vibration through the fingertip.
At higher frequencies, the flexible structure can vibrate rapidly enough to generate audible sound.
The researchers demonstrated audible feedback from roughly 500 Hz up to 20 kHz, covering a large portion of the human hearing range.
This creates a simple way to switch between tactile and audio feedback.
For example, one electrical signal could make the button feel like a physical press, while another could produce an audible confirmation sound.
Why the Ribbon-Shaped Electrodes Matter
The electrode design also makes the technology useful for interfaces containing multiple virtual buttons.
Because the top and bottom electrodes are divided into ribbon-shaped active regions, different electrode pairs can receive different electrical signals.
This means several areas of the same polymer film can potentially be operated independently.
The approach could therefore be adapted for interfaces where multiple touch buttons need different feedback.
Another advantage is its thin and flexible structure.
The researchers report that the skinny button can be integrated with capacitive, resistive, or inductive touch sensors without physically interfering with their operation.
That could make it suitable for devices where adding a bulky motor or conventional mechanical switch would be impractical.
The “Click” Sensation Without a Mechanical Switch
The ultimate goal is not simply to make a touchscreen vibrate.
It is to recreate the familiar “click” sensation of a physical button.
When users press a mechanical button, several signals reach the senses almost simultaneously: physical movement, tactile force, vibration, and sound.
The new skinny button attempts to reproduce this multimodal experience electronically.
A user could press a virtual button and receive a localized tactile response through the fingertip while also hearing an appropriate sound.
This could make flat touch interfaces feel more responsive and provide users with clearer confirmation that their input has been detected.
Designs Can Be Adjusted
The researchers also investigated different designs that can modify the mechanical characteristics of the skinny button.
Properties such as stiffness and pressure sensitivity can be adjusted depending on the structure.
This is important because different applications may require different sensations.
A smartphone interface, vehicle control panel, medical device, and industrial machine could all require different levels of tactile response.
The ability to modify the mechanical properties could therefore help adapt the technology to different applications.
Where Could This Technology Be Used?
The technology could potentially be useful in many modern touch interfaces.
Smartphones and tablets could use it to make virtual buttons feel more physical. Vehicle dashboards could provide tactile and audio confirmation without adding large mechanical switches. Home appliances and industrial control panels could also benefit from localized feedback.
It could even be useful in future flexible or ultra-thin electronic devices, where conventional motors and mechanical buttons may be difficult to integrate.
However, further development would be needed before such systems become common commercial products. Factors such as durability, power consumption, manufacturing complexity, response consistency, and integration with real-world devices would all matter.
A Step Toward More Natural Touch Interfaces
The work by Quang Van Duong and his team demonstrates a different way to approach haptic feedback.
Instead of relying on a bulky motor or requiring the user's finger to slide across a surface, the skinny button uses finger pressure, a localized electric field, and electrostrictive deformation of a thin polymer film to generate vibration.
By controlling the frequency of the electrical signal, the same structure can provide either tactile sensations or audible feedback.
The result is a thin, flexible interface designed to bring back something that modern touchscreens largely removed: the satisfying and informative feeling of a click.
If this approach can be successfully scaled and integrated into commercial electronics, future touch buttons may no longer need to choose between the sleekness of a flat touchscreen and the feedback of a physical switch.
Reference: Van Duong, Q., Nguyen, V.P., Luu, A.T. et al. Audio-Tactile Skinny Buttons for Touch User Interfaces. Sci Rep 9, 13290 (2019). https://doi.org/10.1038/s41598-019-49640-w
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